Moca should work fine for you, barring no difficulties with your coax network. Picking up a POE filter (point of entry) is always a good idea. It blocks foreign signals from coming in, keeps your Moca networking signal inside your house and essentially limits the size of the network that you are trying to drive the Moca signal over. Tivo.com and ebay are two good sources.

Simply setting up the Roamio and mini will both require several connections back to tivo for fairly large transfers to download channel data, software updates and guide info.

How does your Clearwire setup function? As simply a wireless hotspot that connects to 3g/4g and provides wifi, or does it provide wired ethernet as well? (they seemed to have offered both as options)

If cost is critical, in some areas you can get DSL pretty dang cheap (<$20/month). It wouldn't necessarily be fast enough to say, stream HD from netflix, but Comcast on demand would work (the internet connection queues up the show, but the tivo actually tunes to a "channel" on your cable tv as opposed to streaming it) as well as pretty much all the functionality listed below...

What happens without a real-time internet connection with Roamios: (typed on the fly so I might forget a few things!)

The roamios and minis constantly connect to the internet to download images for shows, get extended info on shows, etc to populate the user interface. Roamios used to get really grumpy when losing its real-time connection, though its a little less pissy with the later software updates. You'll have to get used to seeing big error messages such as "temporary service connection issue (C133)" with a long explanation across the top of the HD menu screens as well as empty areas where show data would be in some areas.

Some areas of the user interface will simply be greyed out, such as "what to watch now", "browse tv and movies" "search" <- this last one is a huge loss imho

A full time internet connection supports being able to use the IOS and Android apps to manage shows from outside the home in real-time, or to schedule through tivo.com (with some delay)

Tivo only holds a two weeks ahead on the guide info, so you have to connect in regularly to keep it up to date. It will start to nag you once you get close to running out of data. It also continuously refines the data, as often the data several days out is not exactly correct/complete, so if you rely on old data you will sometimes record multiple copies of shows (comedy central and other cable channels often revise/updates the episode data once you get closer to air date), record at the wrong time and miss a show simply because the data was incorrect originally or miss shows if they are re-scheduled. (sports or other live events in particular, of course)

You also would lose all incoming streaming capability (xfinity on-demand, netflix, hulu, etc), as well as the ability to stream and/or download shows to an IOS (android supposedly coming soon) device out of home. Pretty much all of the other apps (music, opera app store, podcasts) etc are also out of commision too.